Disposable articulated spacing device for surgical treatment of joints of the human body

ABSTRACT

A disposable articulated spacing device for the treatment of joints of the human body, particularly for temporarily replacing an explanted joint prosthesis, comprises at least one first member able to be secured to a first articulation end and at least one second member able to be secured to the other articulation end, both said members being pre-formed and made entirely of biological compatible and porous material suitable to be added with pharmaceutical and therapeutical products. The pre-formed members are reciprocally coupled in an articulated manner to maintain a suitable joint space and at least a partial articulation for the time necessary to perform the further implantation of a joint prosthesis. The biologically compatible and porous material is chosen among metals, metallic alloys, organo-metals, ceramics, glasses, plastics materials, bone cements and combinations thereof. The articulated spacing device maintains a suitable space in the joint seat while allowing considerable articulated mobility, and re-establishes suitable conditions of implantation of a new permanent joint prosthesis.

DESCRIPTION

[0001] 1. Technical field

[0002] The present invention is generally applicable to surgicaltreatment of articulations of the human body and in particular relatesto a disposable spacing device for temporary replacement of jointprosthesis which have to be explanted due to unsuccessful septic oraseptic implantation of artificial joints.

[0003] According to the well known surgical “dual stage” method, theabove spacing device can be maintained in the joint seat as long asnecessary for reestablishing the most favourable conditions ofimplantation of the new artificial joint prosthesis.

[0004] 2. Background art

[0005] It is known how artificial joints, such as knee, hip, heel andelbow joints often have to be removed for various reasons and mainlyfollowing local infections after a surgical implant.

[0006] In such a case, it is not possible to replace immediately theunsuccessful prosthesis with a new one, but the seat of the joint mustbe treated with suitable antibiotics before a new surgical operation canbe performed.

[0007] In the meantime, the space within the joint must be maintained inorder to prevent a reduction in the articular space, retraction of-tietissues, atrophying of the joint and loss of muscular elasticity andtone.

[0008] Spacing devices used in the two-stage implant of artificialjoints, for treatment of both the hip and the knee, are known.

[0009] Italian patent application No. VR95A000072 describes a disposablespacing device for an artificial hip joint, essentially characterized inthat it is made of a biocompatible base material of the type used forbone cements.

[0010] Spacing devices for knee joints which are manually made by thesurgeon at the time of the surgical operation are also known, thesedevices being made from blocks of bone cement of standard shape,optionally containing active constituents.

[0011] A drawback of these known methods of treatment is that they donot allow the space within the joint to be kept apart in anergonomically and anatomically correct manner. Moreover, the long timerequired for preparation increases the difficulties for the surgeon andreduces the probability of success of the operation.

[0012] In order to overcome these drawbacks, spacing devices have beenmade using suitable anatomically and ergonomically shaped moulds whichare filled with bone cement in situ. However, these known spacingdevices do not allow mobilisation of the joint and result in the needfor a long rehabilitation after reimplanting the permanent prosthesis.

[0013] In still other cases, the spacing devices have been obtained bylining a permanent metal prosthesis with bone cement. Although thissolution allows a temporary articulation, it is difficult to prepare andin spite of use of cement-lined prostheses requires that such devicesare positioned in infected seats, which most of the surgeon consider aworsening infection factor.

[0014] DE-A-29703971 discloses a temporary knee prosthesis comprisingthree pre-formed members made of bone cement and impregnated with anantibiotic agent, in accordance with the preamble of claim 1. However,in this prior temporary prosthesis the antibiotic agent is added to thebone cement forming the members during their formation process andtherefore the pre-formed members are initially impregnated with suchmedicaments. Thus, the surgeon has no freedom to choose the specificantibiotic or its amount which are more closely correlated to theparticular patient. Moreover, the prosthesis which is not apharmaceutical product must nevertheless be packaged and stored in asuitable manner to comply with the requirements of the parmaceuticalproducts.

[0015] U.S. Pat. No. 5,980,573 relates to a temporary hip prosthesiscomprising a single pre-formed member failing to provide a completearticulation joint. The base material of the prosthesis is impregnatedwith an antibiotic agent by simply-mixing it in appropriate amount withthe constituent elements of the material during the formation process ofthe member. Although this prior art document provides that theimpregnation of the porous temporary prosthesis may be carried out bysoaking it in a liquid antibiotic, it contains no indication that theimpregnation may be carried out immediately prior of the implantation ofthe prosthesis. In both cases, the pre-formed temporary prosthesis ispre-packaged in a sterile packet or container having indicia or colourcoding indicating the size of the prosthesis contained therein and theantibiotic concentration, thereby excluding that impregnation isaccomplished immediately prior of implantation.

[0016] EP-A-0811359 teaches a method for manufacturing a materialadapted for use as base material for prostheses, which material isformed by a three dimensional structure of band pieces joined togetherwith the interposition of intermediate removable materials to formadjustable hollow spaces. The hollow spaces of the material may befilled with pharmaceutical or therapeutical active products such asantibiotics, hormones or growing agents. However, there is no indicationthat such active products may be added or absorbed in the hollow spacesimmediately prior of implantation of the prosthesis.

DISCLOSURE OF THE INVENTION

[0017] The main object of the present invention is to provide surgeonswith a disposable and ready-to-use articulated spacing device, able tobe directly implanted in the articulation seat for example of knee, hip,hell or elbow joints, in case of replacement of a pre-existingprosthesis which must be removed due to septic or aseptic failures.

[0018] A further object is to provide a disposable articulated spacingdevice which allows to maintain a in a healing environment a suitablearticular space for the time necessary to successfully re-implant a newpermanent prosthesis.

[0019] A further object is to provide a disposable articulated spacingdevice which allows correct articulation and an anatomical and ergonomicform of the temporary implant.

[0020] Yet another object is to provide a disposable articulated spacingdevice which can be easily implanted and explanted into/from thelocation of the joint.

[0021] Yet another object is to provide a disposable articulated spacingdevice with limited articular friction so as to allow considerablemobility of the joint and improve the quality of life of the patientduring hospitalisation.

[0022] These and other objects which will be more apparent hereinafterare achieved by a disposable articulated spacing device for thetemporary replacement of a joint of the human body which, in accordancewith claim 1, comprises at least one first member able to be secured toa first articulation end and at least one second member able to besecured to a second a articulation end, both said members beingpre-formed and made entirely of biological compatible and porousmaterial suitable to be added with pharmaceutical and therapeuticalproducts, said pre-formed members being able to be reciprocally coupledin an articulated manner to maintain a suitable joint space and at leastpartial articulated mobility for the time necessary to perform thefurther implantation of a new permanent joint prosthesis, characterizedin that said pre-formed members are initially free of pharmaceutical andtherapeutical products, said pre-formed members having a porosity intheir base material or suitable cavities formed on their outer surfacesadapted to be filled with pharmaceutical and therapeutical products inthe form of liquid solutions added to the pre-formed members immediatelyprior of implantation thereof either by direct contact and absorption orby insertion thereof in said suitable cavities

[0023] Preferably, the above mentioned biologically compatible andporous material is chosen among metals, metallic alloys, organo-metals,ceramics, glasses, plastics materials, bone cements and combinationsthereof.

[0024] The pre-formed members of the device may be previously chargedwith suitable pharmaceutical and therapeutical products. As alternative,the pre-formed members are initially free of the same products and areadded immediately prior of their implantation by contact absorption orby filling of suitable cavities formed on their other surface.

[0025] Advantageously, the pharmaceutical and therapeutical products maybe chosen among medical active principles, antibiotics and radiopacifierand may be added in the pre-formed members

[0026] In case that the articulated spacing device replaces a kneejoint, the pre-formed members may comprise a femoral member consistingof a body substantially shell-shaped and reproducing the femoralcondyles, and tibial members consisting of a prismatic body able toreplace the resected tibial flat portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further features and advantages of the invention will be moreclearly understood in the light of the following detailed description ofa disposable articulated spacing device furnished by way of anon-limiting example with the aid of the accompanying drawings, inwhich:

[0028]FIG. 1 shows a front view of a first detail of a spacing modelaccording to the invention;

[0029]FIG. 2 shows a side view of the detail according to FIG. 1;

[0030]FIG. 3 shows a top view of the detail according to FIG. 1;

[0031]FIG. 4 shows a front view of another detail of the spacing deviceaccording to the invention;

[0032]FIG. 5 shows a side view of the detail according to FIG. 4;

[0033]FIG. 6 shows a top view of the detail according to FIG. 4;

[0034]FIGS. 7 and 8 show perspective views, from the top and bottom, ofthe detail of the device illustrated in FIGS. 1 to 3;

[0035]FIGS. 9 and 10 show a side view and a top perspective view of thedetail according to FIGS. 4 to 6;

[0036]FIG. 11 shows a perspective view of the two details of thepreceding figures in aligned positions; and

[0037]FIG. 12 shows a side view of an alternative embodiment of thespacing device according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] With reference to the above mentioned figures, there is shown adisposable articulated spacing device for the temporary replacement of ajoint prosthesis explanted from a human body.

[0039] The articulated spacing device, generally indicated with thereference number 1, comprises at least one first member 2 able to besecured to a first joint end and at last one second member 3 able to besecured to a second joint end.

[0040] According to the invention, both members 2, 3 are pre-formed andentirely made of a biological compatible and porous material and aremutually coupled in an articulated manner so as to maintain in a healingenvironment a suitable joint space and at least partial mobility of thejoint for the time necessary to permit the further re-implantation of anew permanent joint prosthesis.

[0041] Preferably, the biological compatible and porous material may bechosen among metals, metallic alloys organo-metals, ceramics, glasses,plastics materials and combinations thereof.

[0042] Specifically, the above plastics material may be chosen amongthermoplastic polymers, such as acrylic resins, polyethylene,polypropylene, thermoformable e.g. by blow moulding or injectionmoulding.

[0043] As alternative, the plastics material may be chosen amongcold-formable resins curable by means of free radical polymerisationsuch as acrylic resins and polyesters.

[0044] In a per se known manner, free radical polymerisation may beaccelerated either by suitable chemical catalysts and initiators, suchas benzoyl peroxide, or physical accelerators such as ionizingradiation, gamma-rays, UV-rays.

[0045] In the particularly preferred embodiment the biologicalcompatible and porous material forming the members 2, 3 is abone-cements, e.g. that used in the Italian patent application no.VR95A000072 filed by the same applicant.

[0046] The pre-formed members 2, 3 may be previously added with suitablepharmaceutical and therapeutical products chosen among active medicalprinciples, antibiotics and radiopacifiers.

[0047] In alternative, the pharmaceutical and therapeutical products maybe added to the pre-formed members immediately prior of implantationthereof either by direct contact absorption or by filling of suitablecavities formed on their outer surfaces.

[0048] The pharmaceutical and therapeutical products in the form ofliquid solutions may be easily absorbed by the device thanks to theporosity of their basic material and then released after implantation inthe joint seat.

[0049] Advantageously, the pre-formed members 2, 3 may be shaped indifferent sizes to be correctly adapted to the different patients.Moreover, these members may present anchoring means for their fixationto the joint ends.

[0050] The embodiment of the spacer device 1 shown in the figures isdesigned to be inserted in the knee joint.

[0051] The pre-formed member 2 is a tibial member and the pre-formedmember 3 is a femoral member.

[0052] In particular, the femoral part 3 consists of a first proximalbody 4 designed to occupy the space left by an explanted metalprosthesis. Preferably, the body 4 has a shape, in plan view,approximately in the form of a “U” or horseshoe, with side portions 4′,4″ and a central recess 5. The external contact surface 6 of the body 4has a curvature able to reproduce that of the femoral condyles.

[0053] The tibial member 2 consists of a second proximal body 7 which isapproximately prismatic, slightly curved and of suitable thickness. Thebody 7 also has a shape, in plan view, approximately in the form of a“U” or horseshoe, with a curved internal contact surface 8 and aninternal recess 9 so as to simulate the resected tibial flat portion.

[0054] The contact surfaces 6, 8 of members 2, 3 are formed so as toallow a roto-translatory movement during the flexing/extending movementof the limb.

[0055] Moreover, the surfaces 6, 8 may have an excellent surface finishwith a low coefficient of friction so as to allow a considerably degreeof articular mobility.

[0056] Both members 2, 3 may be provided with respective projections orrod-shaped distal portions 10, 11 for securing to the respective jointends, e.g. by means of bone cement.

[0057] In use, the surgeon initially removes the previous infected jointprosthesis and cleans the articulation space. The surgeon furtherchooses the suitable spacing device with pre-formed members 2, 3 adaptedof the size of the patient.

[0058] If the pre-formed members are already previously charged withactive principles and pharmaceutical and therapeutical products uponformation thereof, the surgeon implants them taking care that they arefixedly secured to the joint ends and are mutually articulately coupledto allow at least partial mobilisation of the joint.

[0059] If on the contrary the members are not yet charged as above, thesurgeon either impinges them in a solution of active principles or fillswith them several outer cavities formed in situ or pre-shaped on theirouter surfaces, and finally implants the members in the articulationseat, securing them to the joint ends through appropriate anchoringmeans or bone cement.

1. A disposable articulated spacing device for the treatment of jointsof the human body, particularly for temporary replacing an explantedpermanent joint prosthesis, comprising at least one first member (2)able to be secured to a first articulation end and at least one secondmember (3) able to be secured to a second a articulation end, both saidmembers (2,3) being pre-formed and made entirely of biologicalcompatible and porous material suitable to be added with pharmaceuticaland therapeutical products, said pre-formed members (2, 3) being able tobe reciprocally coupled in an articulated manner to maintain a suitablejoint space and at least partial articulated mobility for the timenecessary to perform the further implantation of a new permanent jointprosthesis, characterized in that said pre-formed members (2,3) areinitially free of pharmaceutical and therapeutical products, saidpre-formed members (2, 3) having a porosity in their base material orsuitable cavities formed on their outer surfaces adapted to be filledwith pharmaceutical and therapeutical products in the form of liquidsolutions added to the pre-formed members (2, 3) immediately prior ofimplantation thereof either by direct contact and absorption or byinsertion thereof in said suitable cavities.
 2. Spacing device accordingto claim 1, characterized in that said biologically compatible andporous material is chosen among metals, metallic alloys, organo-metals,ceramics, glasses, plastics materials, bone cements and combinationsthereof.
 3. Spacing device according to claim 2, characterized in thatsaid plastics material may be chosen among thermoplastic polymers, suchas acrylic resins, polyethylene, polypropylene, thermoformable e.g. byblow moulding or injection moulding.
 4. Spacing device according toclaim 2, characterized in that plastics material are chosen amongcold-formable resins.
 5. Spacing device according to claim 1,characterized in that said biological compatible and porous material isa bone cement.
 6. Spacing device according to claim 1, characterized inthat said pharmaceutical and therapeutical products are chosen amongactive medical principals, antibiotics and radiopacifiers.
 7. Spacingdevice according to claim 1, characterized in that said pre-formedmembers (2, 3) are configured so as to allow a roto-translatory movementof the condyles during the flexing/extending movement of the limb. 8.Spacing device according to claim 7, characterized in that saidpre-formed members (2, 3) have respective contact surfaces (8, 6) with aminimum coefficient of friction so as to allow a high degree ofarticular mobility.
 9. Spacing device according to one or more of thepreceding claims, characterized in that said pre-formed members (2, 3)are shaped in different sizes to be adapted to any patients.
 10. Spacingdevice according to claim 1, characterized in that said pre-formedmembers (2, 3) are provided with anchoring means for attachment thereofto the joint ends.
 11. Spacing device according to claim 10,characterized in that said anchoring means consist of respectiveprojections or rod-shaped distal portions (10, 11).
 12. Spacing deviceaccording to claim 1, characterized in that said pre-formed members (2,3) are securable to said joint ends with bone cement.
 13. Spacing deviceaccording to one or more of the preceding claims, particularly for kneejoint, characterized in that said pre-formed members (2, 3) comprises afemoral member (3) and a tibial member (2).
 14. Spacing device accordingto claim 13, characterized in that said femoral member (3) consists of afirst body (4) substantially in the shape of a shell to reproducefemoral condyles and that said tibial member (2) consists of a secondbody (7) of substantially prismatic shape with predetermined thicknessto replace the resected tibial flat portion.